Boom Supersonic has received an FAA experimental certificate of airworthiness for its XB-1 technology demonstrator, clearing the way for flight testing to get underway at Mojave Air and Space Port, California.

The FAA’s permit to fly the 71-ft.-long, delta-winged aircraft comes as Boom begins high-speed taxi tests, with a run up to 60 kt. achieved on Aug. 23. Previously the XB-1 achieved a top taxi speed of 10 kt. at Boom’s site in Centennial, Colorado, before the aircraft was transferred to California for the flight-test program earlier this year.

“This forms part of the build up to the flight-test campaign that we still expect to start later this year,” Boom Founder and CEO Blake Scholl says. Speaking to Aerospace DAILY, he adds: “Over the next few months we’re going to continue to expand the envelope and push to higher speeds out on the runway. When we have enough tests in a row where the team comes back and says, ‘If we’d flown today it would have been a really good day,’ that’s when we know it’s going to be time to push the throttle forward and pull back on the stick.”

Configured with three afterburning General Electric J85-15s, the slender delta-winged XB-1 is intended to pave the way for Boom’s full-scale Mach 1.7 Overture airliner by proving out design processes, engineering software, digital modeling, production methods and flight-test procedures. Boom says the XB-1 therefore remains highly relevant, despite the company’s 2022 announcement of a complete redesign of the Overture airliner with four engines and a cranked-arrow planform in place of the original trijet, ogive-wing configuration.

The length of the test campaign and progression to Mach 1-plus flight is still to be determined, Scholl says. “It really depends greatly on how things go. It’s hard to see a way that we will go from first flight to first supersonic flight in less than three months. It could be as long as a year and we’re going to let the airplane tell us when it’s ready,” he says. Boom originally hoped to fly the XB-1 in 2021, but delayed the effort after integration and initial ground tests took longer than expected. 

The XB-1 program also has been key to the company’s safety culture, Scholl says. “In the tech world, people talk about ‘move fast and break things’—and we want to move fast. We definitely don’t want to break them.”

Boom has also filed its request for special authorization with the FAA for supersonic flight. Although designed for Mach 2.2, the planned cruise speed of the original Overture trijet, the XB-1, is now targeted at a top speed closer to the revised Mach 1.7 of the later configuration. “It’s unlikely we will push XB-1 that high [Mach 2-plus]. What we really want to see are the low-speed handling qualities, which are actually one of the most difficult things to get right on a long, skinny airplane,” Scholl says.

“We want to see if they are as we expect them. And then we’ll go fly the airplane supersonic. We’ll make a call later on how far we want to push the limits to the top speed,” he adds.

On preparations for the Overture, Scholl says progress on the company’s 400,000-ft.2 production and test facility at Piedmont Triad International Airport near Greensboro, North Carolina, is moving slightly ahead of schedule. “We said we’d be ready next year, and it looks like it might be ready earlier next year than we thought it would be. It’s looking like a real factory now. The sidewalls are up for about half the building and it’s coming along.”

Boom also recently announced that former Boeing propulsion veteran Scott Powell has joined the company as senior vice president for the Symphony engine program for Overture. Powell, who is now responsible for leading the development, industrialization, certification and integration of the propulsion system, was formerly engineering propulsion leader for the 787 and held key engine-related roles in the KC-46A tanker program among others. Most recently, he served as the Propulsion Integrated Product Team leader for the B-52J Commercial Engine Replacement Program.